Antiskinning and weather resisting agent for drying oil compositions



Patented June 30, 1942 ANTISKINNING AND' WEATHER RESISTING AGENT FOR DRYING OIL COMPOSITIONS Harold C. Reynolds, JnjElizabeth, N. J.,

to Standard Oil Devel poration of Delaware assignor opment Company, a cor- No Drawing. Application October 22, 1938,

Serial N0. 236,579

7 Claims.

The present invention relates to anti-skinning and anti-oxidizing agents in drying oils, paint and varnish compositions. More particularly, the invention relates to includes, as-its object, the addition thereto of aliphatic and aromatic cy'anamides which possess the characteristic property of retarding the premature oxidation of drying oils, paints-varnishes, enamels and th like. Furthermore, these organic cyanamides possess the additional characteristic property of interrupting the continued oxidation of drying oils, paints, enamels, varnishes and the like after said products have reached the desired oxidized condition thereby increasing their durability.

In the manufacture of paints and varnishes, including the incorporation of drying oils therein, it is customary to employ a suitable quantity. of an oxidation catalyst to speed up the normal drying rate of the oil so that the composition will dry hard within a reasonable time after it is spread on a surface in a thin film. This positive oxidation catalyst is commonly called a dryer. It is well known that dryers commonly employed in-v duce various oxidation phenomena, some of which are necessary and desirable, and some of which are very objectionable.

The development of the quick drying coating compositions has been attended with difficulties connected with the tendency of these coating compositions to change consistency on storage and to gel and skin on standing in the closed container or when the container cover is removed and the container exposed to the air. When' these quick drying varnishes, paints or enamels are applied over surfaces, they also have the tendency, upon drying and after slight weathering action, to show cracks, roughness, brittleness, peeling and a general breakdown of the film structure. The breakdown of a drying oil film may be due to brittleness caused by oxidation products or to a peculiar gel structure which depends, probably, upon the manner of cooking the resin and drying oil if the drying oil composition is a varnish. If the oil-resin mixture is cooked for too long a period, the gel structure formed maybe of a type which will not weather satisfactorily.

According to the present invention, these undesirable qualities, such as skinning, gelling and subsequent oxidation, are eliminated and films of greater durability are obtained by adding into drying oil compositions and efliciently as anti-skinning agents. However, di-

' can be purchased in various grades, all of which when mixed with-varnishes.

- ganese and 0.01%

paints, varnishes, oils and the like a small quantity of an organic cyanamide. It is apparent from the-results obtained by practicing this invention that all organic cyanamides will functign very appear to be of about the same degree of efficiency. These guaiacol products have a rather disagreeable odor and for this reason. only small quantities can be used. But, quantities greater than 1.0% cannot be employed without sacrificing rapid drying when added to quick drying varnishes. Lower percentages, such as 0.1%, only inhibit the skinning for 19 days.

Pyrocatechol is also a very powerful anti-skinning agent, as low as 0.1% appeared to prevent skinning tothe sanie degree as ten times the However, amounts of pyrocatechol greater than 0.1%

amount of guaiacol.

interfere with rapid drying. Its odor is rather pleasant and somewhat Its principal drawback analogous-to guaiacol. is its darkening effect As a specific example of an embodiment of this invention, a varnish which had a pronounced tendency to skin was prepared according to 'the' following formula:

Varnish formula Modified phenolic resin lbs 100 China-wood oil gals Petroleum thinnen gals Dryers equivalent to 0.4% lead: 0.03% mancobalt based on the weight of drying oil.

Procedure The oil and pounds of the resin were heated to 550 F. for thirty minutes. The balance of the resin was added and the varnish cooled to 450 F. and thinned with the mineral spirits. When the thinned varnish reached room temperature, 5.5 lbs. of mixed dryers were added thereto. The material thus obtained was a very rapid drying varnish which contained substantially 51% of non-volatile matter, and when flowed on a clean wooden panel, dried hard to touch in 3 hours.

To gram portions of the finished varnish prepared in the manner described above, 0.2% of di-n butylcyanamide, based on the non-volatile content of the varnish, was added. Small' pronounced and uno-meter for a period of about 11 weeks). The eye vials were iilled about half-full with these varnish portions, using 2 vials (2 oz. and 4 oz.) for each test. Samples of the untreated varnish were likewise included for comparison Thevialswere stoppered and examined for skinning at regular intervals. To those samples, both treated and untreated, which did not skin at the end or 4 days, a fresh supply of air was admitted. A skin was considered to have formed when it had sufflcient strength to support the varnish when the vials were inverted. This type of accelerated test is equivalent to several weeks or months for varnishes packed in cans with the usual small air space which is allowed, provided the 'cans are not opened until the contents are to be used. At the end of 4 days the non-inhibited varnish in both the 2 oz. and 4 oz. bottles formed a skin.

After 25- days the inhibited varnish did not form a skin in either the 2 oz. or the 4 oz. bottles.

Inhibited varnish samples, which showed no skinning after standing 9. month, were flowed over a clean wooden .panel. Samples of the untreated varnish were also flowed over in the same manner on identical panels for purposes of compariscn. The dried panels of the treated and non-treatedvarnish were exposed in a Weathercycles (equivalent to used in this artificial weathering apparatus consists of the following weather conditions every 24 hours, which istaken as a cycle:

Ram- 1 Rain v v 2 Light la Blank... 1

Total 24 After 76 cycles in the 'WeatherPo-meter the panels coated with the uninhibited varnish showed cracks, roughn s. peeling, brittleness and other usual undesirable weathering characteris tics, whereas the panels coated with the inhibited varnish did not exhibit any of the undesirable characteristics but showed a marked improvement in the durability, thus indicating that the inhibitors counteracted the undesirable oxidation eflects in the latter stages of thedrying process, thereby increasing thevarnishfllm tiurability'x-and counteracting "the wrinkle formation by retarding superficial. bxidation.

' The anti-skinning agents of this invention may be employed in practically any type of drying oil composition, such as P ints, enamels, varnishes,

to 0.5%. Their action in drying oils is to inhibit the action of gaseous oxygen when confined in containers, interrupt the induction period (superficial peroxide formation) until the normal oxidation rate has progressed to the desirable stage oLdrying, and retarding subsequent oxidation thus extending the life of the film.

These anti-skinning agents mix readily with hibitors in tung oil varnish cooking. They mix readily in paints, enamels, etc. They do not increase the viscosity or give any false body. Their added advantages are their light color and mild odor, thus preventing the darkening or coloring of light straw colored varnishes. They do not react betweendriers such as lead, cobalt and manganese in that'they act as neutral bodies in varnishes, enamels and the like.. 1 While the preferred embodiment of this invention has been disclosed, it will be readily apparent to those skilled in the art that many changes and variations may be made therein without departing from the spirit of the invention.

.I claim:

1. A coating composition containing a drying oil, a positive oxidation catalyst and, as a negative oxidation catalyst, a hydrocarbon substituted carbamonitrile .in sufficient quantity to substantially prevent oxidation. got-the composition .in the packaged state without materially retardoil, an oil-soluble resin, a dryer and an oxidation inhibitor consisting of .di-n-butylcyanamide.

3. A coating composition containing a drying oil, an oil-soluble resin, a dryer and an oxidation inhibitor consisting of 0.2% di-n-butylcyanamide. 4. A drying oil coating composition containing a drier and having incorporated therein from etc., as well as in the dryingoils used in their manufacture. When used as oxidation inhibitors in drying oils, the quantity may be from 0.01%

0.01%" to 0.5% oil-a hydrocarbon substituted carbamonitrile.

5. A drying oil coating composition containing a drier; and'zhaving-incorporated therein from 0.01% to 0.5% di-n-butylcyanamide.

0. A. method tor preventing the formation of ,scuin orskin-on the surface of a packaged drying oil compositioncon Y 'gadrier which com;- prises fincorporiting a hydrocarbon substituted 

